A long term evolution (LTE) technology is long term evolution of a universal mobile telecommunications system (UMTS) technology standard formulated by the 3rd generation partnership project (3GPP) organization. Key transmission technologies such as multiple-input multiple-output (MIMO) are introduced into an LTE system. Therefore, spectral efficiency and a data transmission rate are significantly increased. By means of a transmit precoding technology and a receive signal combination technology, a MIMO-based wireless communications system can obtain diversity and array gains. The MIMO-based wireless communications system needs to perform precoding processing on a signal. A signal transmission function based on precoding may be expressed as:y=H{circumflex over (V)}s+n, 
where y represents a received signal vector, H represents a channel matrix, {circumflex over (V)} represents a precoding matrix, s represents a transmitted signal vector, and n represents a measurement noise. The transmitted signal vectors on a transmit end passes through the precoding matrix {circumflex over (V)} for precoding, and a precoded matrix is obtained. The precoded matrix passes through the channel matrix H, the measurement noise n is added to the precoded matrix, and then the received signal vector y is received on a receive end.
To implement optimal precoding, a transmitter usually needs to obtain channel state information (CSI) in advance. The transmitter and a receiver may be respectively a base station device or a terminal device. In a downlink data transmission process, the transmitter may be a base station device, and the receiver may be a terminal device. A commonly used method is that the terminal device quantizes instantaneous CSI and reports the CSI to the base station.
The CSI information reported by the terminal includes rank indicator (RI) information, precoding matrix indicator (PMI) information, channel quality indicator (CQI) information, and the like. An RI may be used to indicate a transport layer quantity and a precoding matrix {circumflex over (V)} that are used for data transmission. A PMI may be used to indicate the precoding matrix {circumflex over (V)} used for data transmission. Herein, a precoding matrix V may be determined first by using the PMI, and then {circumflex over (V)} is indicated according to the RI or a determined rule.
In some 3D MIMO (3 Dimension MIMO) scenarios, on one carrier, PMIs of two precoding matrices need to be fed back, to respectively indicate a precoding matrix in a vertical direction and a precoding matrix in a horizontal direction. A precoding matrix may be indicated by using a Kronecker product of a precoding matrix in a vertical direction and a precoding matrix in a horizontal direction. A precoding matrix V1 may be expressed as follows:V1=AB, 
where  indicates a Kronecker product. A size of the matrix V1 is determined by row and column quantities of a precoding matrix A in the vertical direction and row and column quantities of a precoding matrix B in the horizontal direction. Herein, A may also represent a precoding matrix in the horizontal direction, and correspondingly, B represents a precoding matrix in the vertical direction.
Usually, dimensions of A and B are determined by an antenna port quantity. In a process of selecting a codebook, a precoding matrix set needs to be further determined according to a distribution status of antenna ports. User equipment and a base station determine different codebook sets for different antenna port configuration manners. The UE or the base station needs to store the different codebook sets, causing waste of storage resources.